package ch6;

/**
 * @author ANG.YU
 * @date 2020-08-11 17:31
 */
public class Instrument {
    static void tune(Instrument i) {
        i.play();
    }

    public void play() {
    }
}

class Wind extends Instrument {
    public static void main(String[] args) {
        Wind w = new Wind();
        Instrument.tune(w);
    }
}
